Air-control means for mechanical stokers



, 1,620,672 March c. F. MILLER AIR CONTROL MEANS MECHANICAL STOKERS Filed May 10, 1925 it 4 25 C) .VIIIIIIIII'IIIII v arL l L zler WITNESSES: F 6 INVENTOR 5y y g 7 a5 7 56 ATTORNEY PATENT OFFICE.

CHARLES E. MILLER, OF MOORE, PENN$YLVANIA, ASSIGNOR TO WESTINGHOUSE EECTEIG AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

AIR-CONTROL MEANS FOR MECHANICAL STOKERS.

Application filed May 10, 1923. Serial No. 638,129.

ject to provide apparatus of the character designated which shall be effective to automatically restrict the air supply to all or to any portion of the fuel bed of a stoker upon a tendency for the passage of an excessive amount of air through the fuel bed or through a portion thereof.

In the accompanying drawing, Fig. 1 is a side view, in section, of a mechanical stoker of the forced-draft, underfeed type, illustrating one form of my invention, dampers being diagrammatically represented; Figs. 2 and 3 are perspective views of two types of damper plates ada ted to be operated .in

. the Stoker of Fig. 1; ligs. 4 and 5 are front views, partially in section and partially in elevation, showing the method of installation of the damper lates shown in Figs. 2' and 3 respectively; Fig. 6 is aside view, in section,.of a modified form of damper plate adapted to give a stream line elfect; and

Fig. 7 is a detailed sectional view taken on line VIE-VII of Fig. 5 illustrating the ad: iusting means employed in the dampers of Figs, 2 and 3. p

in the operation of mechanical stokers, it frequently happens that the .fuel bed becomes so thin at a given point as to admit an excessive amount of air therethrough, resulting in extremely rapid combustion and the actual formation of a hole through the fire. This is an extremely undesirableefiect, inasmuch as it robs air from the remainder of the fuel bed, overloads the air supply means in a forced-draft stoker, and produces dilution of the line gases.

In accordance with the present invention, I preferably form the air supplying tuyeres in a mechanical stoker into a plurality of groups, each with its own air supply duct, and I then place in each duct a swinging apron or damper which normally alfords but little opposition to the air flow, but the arrangement is such that, when the velocity of air flow tends to exceed a predetermined amount, said damper moves to largely or wholly out ch" th air flow through the associated duct. By this means, if a hole is burned through the fuel bed, the resultant rapid flow, of air through the duct supplying said portion of the fuel bed operates the automatic damper or dampers associated therewith and prevents the excessive flow of air through the hole.

Referring to the drawing for a more detailed understanding of my invention, I show the tuyeres of a mechanical stoker of the forced draft underfeed type at 10 in Fig. 1. Below and'to the rear of these tuyeres is anextension grate 11 followed by a live dump grate 12, all of usual and'vlell-known I YP 1 it 1 Air is supplied to the stoker through a main duct 13 from any suitable source underthe control of a manually operated damper 14, andpasses into a plenum chamber 15; Suitable diaphragms 16, 17, 18 and 19 form ducts 20, 21 and 22, the duct 20 supplying the lower portion of the main tuyeres, the

duct 21 supplying the extension grate 11, and the duct 22 supplying the dump grate 12. Mounted'in the entrance to the duct 20 is a swinging damper 23, illustrated more in detail in Figs. 2-5 inclusive. In; the

form shown in Fig. 2, a plate 24 is provided with outwardly extending arms 25 and 26 having knife edges on their lower side as indicated, the arms'25 and 26 .being'somewhat above the center of gravity of the plate 24. As shown in Fig. 4, the plate 24 is mounted in the opening into a duct with the arms 25 and 26 rest-ing in suitable openings in the walls of the duct so that said plate is free to swing therein.

Inasmuch as considerable difficulty would be encountered in installing or removing the plate 24 from an assembled stoker, I prefer to employ the damper shown in Fig. 3-in which a plate 27 is provided with notches 28 and 29 in the edges thereof, said notches being shaped to a knife edge in their upper surface as shown at 30 to format knife edge support. By referring toFig. 5, it will be noted that-the plate 27 ismerely hung in arc-shaped lugs 37 extending from the side walls of the duct to be controlled, it beingobvious that a damper plate of this form may be readily inserted into, or removed from, an assembled stoker.

Reverting to Fig. 1, it will be noted that the damper 23 is so mounted in the opening into the duct 20 that normally there is an extended opening 30 between the lower edge thereof and the right-hand end of the diaphragm 17, thus permitting free entrance of air into the duct 20 However, should a hole bum through the fuel bed over the lower tuyeres of the group 10, the excessive rate of air flow from the plenum chamber through the duct would cause the damper 23 to swing in' a Clockwise direction,

largely closing off the passage. and re stricting the air supply to the tuyeres in questio e v u A similar damper31 is mounted to operate upon the air passing through the duct 21 to tha -extension grate l1- and still another damper-'32 is efiective to operate upon the air passingfthrough ,theduct'22 to the dump grate 12'. I also-show a manually operated damper for further controlling the air supply to the duct 21 and an additional'nian-i ually controlled damper 34 for air fiOW'i'Il the duct 22. Y

It is desirable that the critical operating point of the automatic dampersthus de-- scribed should be susceptible ofa'd justment adjusting the and accordingly I may provide abolt 34,

as shown more clearly in Fig. 7, this bolt projecting through the central .portion of the damper plate; and beingthreaded throughout" substantially its entire length w'it'lisuitable lock 'nutson opposite sides of the damper plate, the bolt; being prov-ided with .a weighted head 40. l Obviously by longitudinaladjustment of this bolt, the center of gravityof the damper assembly maybe' adjusted in a direction transverse to'the plane ofthe plate, thus causing the damper plate to assume an oblique position of rest, such asthat indicated in Big. 7. By the use of this adjustment on the damper 23 of Fig. -1,.the opening 30 may :be' increased or decreased, together with the critical air velocity to which the damper will swing to plied to but a'port'ion of the tuyeres in anrestrict the air flow.

' Inasmuch asvtheair supply may be to some extent impeded by reason of the eddies formed around the edge of a fiat plate, I- may desire to employ a damper :member of the form-shown at 35 in F ig; 6, the

. cross section being-oval-snaped with the end having a small; radius of curvature pro ect,--

ingupwardly; Theair passage 36 provided thereunder is-of such configuration as to' establish little' or no eddying effect but,

' nevertheless, upon the attainment of a predetermined high air velocity, the damper 35- will swing toiiestrictthe air supply as in the foregoing cases. i 1

While I haveshown my inventionasapunderfeed Stoker of. the forced-draft type, it willbe obvious that it is not so limited:

but that I may apply it with equal efiectiveness to any other type of stoker, and upon either forced-draft or natural draft.

While I have not shownautomatic air control to the upper tuyeres 10 because of the thickness and greenness of the iire at this point with attendant small liability to velocity tends to exceed a predeterminedamount, and means for laterally altering the "position of the center of gravity ofeach swinging damper assembly, "whereby the criticalv opera-ting points of said assemblies may bealtei ed With'respect to each other.

A T2. 111 a stoker embodying-a plurality of groupsof tuycres, each group having an air supply duct thereto, swinging dampers respectively mounted in said ducts and adapted to restrict air flow therethrough whenthe air velocity tends-to exceed a predetermined vamount, an" elongated member 'mountedon each of the dampers and transversely to the axis thereof, and means permitting longitudinal adjustment of said members whereby'the location of the centers of gravity offsaid damper assemblies and the critical operatingpoints of said dampers are altered-with respectto each othenf 3. The combination with. a forced-draft stoker embodying a' plurality of groups of tuy'ei'es, each group with its separate air" supply duct, of means for'establishing a predetermined relation of air pressures at-wthe respe tive tuyere groups, and means? for restrict ng the airfiow- 1n at least one of.

the ducts when the air velocity tends to eX-- ceed a given'pre-determined velocity. j

4. 'Thecombination with a forced-draft stoker embodyinga plurality of groups of "tuyres, each group withits separate air supply duct, of means for establishing a predetermined relation of air pressures at the respective tuyere groups, and means for restricting the air flow in any one of said lit) :ducts when the air velocity 'in' said duct tends to exceed a pie-determined maximum velocity established for said duct.

5. The combination with a forced'draftj stoker embodying a plurality of groups of 'tuyere's, each group with its separate air supply duct, of means for establishinga prea determinedrelation of air pressures at the respective tuyere groups, means for restrict ing the air flowin each of said ducts when the air velocity in said-duct tends to exceed a pie-determined maximum velocity estab-' lished for said duct, and means foraltering I the critical operating'velocity in each duct. In "testimony whereof, I; have hereunto subscribed my name this 7th day of .May,

CHARLES F. MILLER. 

